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M24C16, M24C08, M24C04, M24C 02, M24C01
Write Control (WC)
The hardware Write Control pin (WC
) is useful for
protecting the entire contents of the memory from
inadvertent erase/write. The Write Control signal is
used to enable (WC
=VIL) or disable (WC=VIH)
write instructions to the entire memory area. When
unconnected, the WC
input is internally read as
V
IL
, and write operations are allowed.
When WC
=1, Device Select and Address bytes
are acknowledged, Data bytes are not
acknowledged.
Please see the Application Note
AN404
for a more
detailed description of the Write Control feature.
DEVICE OPERATION
The memory device supports the I
2
C protocol.
This is summarized in Figure 4, and is compared
with other serial bus protocols in Application Note
AN1001
. Any device that sends data on to the bus
is defined to be a transm itter, and any device that
reads the data to be a receiver. The device that
controls the data transfer is k nown as the master,
and the other as the slave. A data transfer can only
be initiated by the mas ter, which wi ll also provide
the serial clock for synchronization. The memory
device is always a slave device in all
communication.
Start Condition
START is identified by a high t o low transition of
the SDA line while the clock, SCL, is stab le in t he
high state. A START condition must precede any
data transfer command. The memory device
continuously monitors (except during a
programming cycle) the SDA and SCL lines for a
START condition, and will not respond unless one
is given.
Stop Condition
STOP is identified by a low to high transition of the
SDA line wh ile th e clock S CL is sta ble in the h igh
state. A STOP condition terminates
communication between the m emory device and
the bus master. A STOP condition at the end of a
Read command, after (and only after) a NoAck,
forces the memory device into its standby state. A
STOP condition at the end of a Write com mand
triggers the internal EEPROM write cycle.
Acknowledge Bit (ACK)
An acknowledge signal is used to indicate a
successful byte transfer. The bus transmitter,
whether it be master or slave, releases the SDA
bus after sending eight bits of data. During the 9
th
Table 3. Device Select Code
1
Note: 1. The most significant bit, b7, is sent first.
2. E0, E1 and E2 are comp ared against the respective ext ernal pins on the memory device.
3. A10, A9 and A8 repres ent high significant bits of the address.
Device Type Identifier Chip Enable RW
b7 b6 b5 b4 b3 b2 b1 b0
M24C01 Select Code 1010E2E1E0RW
M24C02 Select Code 1010E2E1E0RW
M24C04 Select Code 1010E2E1A8RW
M24C08 Select Code 1010E2A9A8RW
M24C16 Select Code 1010A10A9A8RW
Table 4. Operating Modes
Note: 1. X = V
IH
or V
IL
.
Mode RW bit
WC
1
Bytes Initial Sequence
Current Address Read 1 X 1 START, Device Select, RW
= ‘1’
Random Address Read
0X
1
START, Device Select, RW
= ‘0’, Address
1 X reSTART, Device Select, RW
= ‘1’
Sequential Read 1 X
≥
1 Similar to Current or Random Address Read
Byte Write 0 V
IL
1 START, Device Select, RW = ‘0’
Page Write 0 V
IL
≤
16 START, Device Select, RW
= ‘0’